This invention relates to automated testing of printed circuit boards.
In the prior art, automated testing of newly manufactured printed circuit boards without components has been accomplished by making electrical connection to a large number of points on the board and then tests for continuity and shorts are performed to locate faults which are then corrected. One approach to making these electrical connections is to use what is known in the art as a bed of nails which is a matrix of contacts having spring loaded conductive probes arranged in rows and columns with a contact typically being spaced from adjacent contacts by 0.100 inches or 0.050 inches. Electrical connection to each of these contacts is via a wire fastened to the rear of each contact and the wires are also connected to switching equipment and test circuitry. Installation of these wires to contacts spaced 0.050 inches apart requires wires having diameters in the order of 0.040 inches including the insulation. Assembly is a relatively costly and time consuming manufacturing operation. In addition, due to the small wire size wire breakage is a problem and repair is difficult due to the large number of wires in a relatively small space. For a tester having contacts spaced 0.050 inches apart, testing a board 3 inches by 5 inches requires 6,000 contacts with wires connected thereto. All these wires must also be attached to relays and other circuitry to establish the connections and perform tests.
Thus, there is a need in the art for a relatively simple, easy to manufacture and inexpensive bed of nails printed circuit board tester.